Telephone system



Jan. y19, 1932. N. H. sAUNDERs TELEPHONE: SYSTEM Original Filed Nov. 25, 1929 Patented Jan. 19, 1932 UNITED lsrn'lfrss PATENT OFFICE vII'OVREIAN H. SAUNDERS, OF CHICAGO, ILLINOIS, ASSIGNOR, BY MESNE ASSIGNMENTS,

TO ASSOCIATED ELECTRIC LABORATORIES, INC., OF CHICAGO, ILLINOIS, A CORPORA- TION F DELAWARE Original application iled November 25, 1929, Serial No. 409,452.

TELEPHONE SYSTEM Divided and this application med March 4, 1931. GSeral No. 520,037.

The present invention relates to telephoney systems employing automatic switching apparatus includingswitches controlled b a master switch; and the object is the pro uc-a tion of a new and improved master s witch 'i which tests for the presence of potential on the respective test conductors of the lines accessible to the lineswitches, instead of testing for the absence of potential as heretofore.

This application is a division of m l copending application, S. N. 409,452, file No` Setting up e desired connection In order to explain the operation of the apparatus shown, including the way the improved master switch cooperates with the selector Sl as it controls the lineswitches such as LS, it will be assumed that the subscriber' at substation A1 desires to make a call.

Zhen the receiver is removed at substation A1, a circuitk is closed across line conductors 101 and 103 for line relay 105through the contacts of the bridge cut-off armature 106` of the lineswitch LS.` Relay 105.0perates and disconnects the. so-called privatenormal conductor 104 from the bridge-cut-oi' winding (the upper winding) of the lineswitch magnet 120 and connects it to ground-V instead, thereby guarding the calling line against seizure by the connectors having access to it. At its lower armature, relay 105 closes a circuit for the lower winding- (the pull-down winding) ofthe magnet 120 over the associated chain conductor'140,at the same time opening the chain as regards the succeeding lineswitehes. It willbe noted that ground3 potential: is supplied the chai-nconductor 140 through contacts in the master switch MS and through the lower winding of the delay relay 154. By way of explanation, it may be pointed out that the delay relay 154 is included in the circuit so. as to delay the operation of a lineswitch for a slight interval followingv the operation of the. line relay so as to give a releasing lineswitch time for the plunger to realign before the lineswitch reoperates, in case it is reoperating irnmediatelyV following its release. The eurrent-fiow through the pull-down windingl over the chain circuit is not suiicient to op.- erate either of the armatures of ma net 120 1 as long as the lower winding of the elay relay is in circuit alone. The upper winding of the delay relay, it will be noted, is. normally short-circuited through the contacts of the' relay, making the relay slow to operatef on account of the fact that its short-circuited winding is on the armature end of the relay. When relay 154 operates, it removes the short circuit from around the upper winding and connects the low-resistance upper winding in parallel with the high resistance lower winding, allowing suiiicient current to flow over the chain conductor 140 to operate both armatures of the lineswitch magnet 120. The bridge-cut-ol' armature 106 operates the associated contacts to disconnect 'ground and line relay 105 from the conductors of the calling line, and the plunger armature 107 operates the bank sprin s 109-113 and also closes the contacts 108. T closing of contacts 108 reconnects the upper winding of magnet 120 to the grounded conductor 104. y

When the contact springs 109-113 .are pressed into engagement with their respective associated contacts, and the connection is thereby extended to the selector S1, the ground potential maintained on conductor 104 by the slow-acting line relay 105 is transmitted to release-trunk conductor 115 and thence over the branch conductor 163' to the master switch MS, displacing the normal battery potential and causing the master switch to preselect another idle trunk in the manner to be describedv hereinafter.

In the selector S1, line relay 121, which is connected to` the conductors 114 and 1'16` through contacts of relay 1241, now energizes over the calling line, upon operating, relay 121, at the normally closed contacts controlled by its upper armature, removes the normal shunt trom around the winding ot release relay 122, at the same time closing a circuit -for relay 122 in series with vertical .magnet 126. As a result ot its operation, release relay 122, at its lower armature, opens a point in the circuit oli release magnet 127 and closes a point in the circuit of rotary magnet 129, and at its inner-upper armature it removes the shunt 'from around the lower winding oi" relay 123 and applies ground potential to release-trunk conductor so as to maintain t` e lineswitch .LS operated thronwh the upper winding et magnet after relay 105 has fallen back. It may be pointed out that current lioi 's through the upper winding` et relay 123 from the grounded conductor 115 prior to the operation o relay 122, but relay 123 does not operate at this time because the lower winding is short-circuited, and because the upper vv'inding is a non-inductive winding. lVhen the short circuit is removed from the lower winding, however, relay 123 operates from the grounded conductor 115, its two windings being connected in series at the vertical-ott-normal contacts 132. Upon operating, relay 23 locks itseliLl operated at its inner-lower zu'mature independent of contacts 132, and at its lower armature it opens a point in the circuit of rotary magnet 129. At its upper armature, relay 123 shunts the upper armature and cooperating contact ot the line relay 121 so as to prepare an operating circuit for the vertical magnet 126.

It will be noted that a connection normally exists between the lower talking conductor 11G ot the selector and the dial-tone transitormer 117, through the contacts associated with the over-flow spring 125, and the lower windingot relay 121. On account o'l this com'iectiou, the tone produced by the dial-tone current heard by the calling subscriber. and he is thereby informed that he ma y now dial the digi ts ot the desired number.

lhen the lirst digit is dialled, the circuit of line relay 121 is opened one or more times at the calling station by means ot the usual calling device (not shown). Each time its circuit is opened, relay 121 Jfalls back, ane at the normally closed contacts controlled by its upper armature short-circuits the release relay 122, and by the same action closes a circuit tor vertical nnignet 126 through the upper contacts ot relay 123. Vertical magnet 126 operates each time relay 122 is shortcircuited and the said magnet restores each time the short-circuit removed ,trom around the winding of relay 122. By the operation of vertical magnet 126, the wipers 133-135 of the selector S1 operate step-bystep until they arrive opposite the desired level ol bank contacts. Relay 121 remains operated while it is momentarily short cire cuited, because of circulating current in its winding.

Each time line relay 121 energizes following its lirst deenergization, ground potential is applied to the junction ot the windings of relay 123 by way ot' olinormal spring 128 and its upper contact, contacts of relay 124, lower armature, operated, of relay 122, lower armature of relay 121, and overflow spring 13 Relay 123 does not fall back when the lower winding is intermittently shunted during the vertical operation of the switch, because of the circulating current in the short circuited lower winding. lVhen the line relay comes to rest, however7 at the end oi' the vertical movement, the lower winding ol relay 123 remains short-circuited, and the relay falls back. At its lower armature, relay 123 completes the circuit ot the rotary magnet 129 through the off-normal contacts 130 and the self-interrupting contacts ol magnet 129. The rotary circuit includes the lower armature operated, ot release relay 122, contacts of relay 124, and ofi-normal spring 128 and its upper Contact,

By the buzzer-like operation of magnet 129, the wipers 133-135 are driven over the.`

contacts in the level selected by the vertical movement.

lNhen an idle contact set is reached (tor example the contact set from which the conductors 13d-138 extend), a battery potential is encountered on the test contact thereof by wiper 134, the conductor 137 being connected to battery through a path correspondingT to the one through which the conductor 115 ot S1 is normally connected to battery, including the inner-upper armature, normal, ol relay 122, vertical-otl-normal contacts 132, and the non-inductive ripper winding ot relay 123. The switch to which 122-121 extend may be similar to the se.- lector S1.

lhen this battery potential is encountered by test wiper 1341, the switching relay 121. whose upper winding is connected between the now grounded conductor 115 and test wiper 134- through the upper contacts ot' relay 122, energizes over wiper 131 and conductor 137. Upon energizing, relay 1211 at its middle lower armature opens the circuit oi'4 the rotary magnet and a point in the circuit o't release magnet 127; at its inner-lower armarconductors relays therein corresponding to relays 121,l 122, and 123 of the selector S1 energize to prepare the switch for operation and to place a ground potential on conductor 137 so as to maintain the selector S1 and the lineswitch LS operated.

In the selector S1, line relay 121 falls back when it is disconnected at the upper and lower contacts of relay 124 .and it again short-k circuits relay 122. The vertical magnet 126 does not respond .at this time owing to the fact that Arelay 123 is at normal. Responsive to being short-circuited, relay 122 falls back and removes the local ground connection from conductor 115 at its inner-upper armature, Vleaving this conductor grounded only by way of ywiper 131 and conductor 137 and at its upper armature it vremoves the short circuit from around the upper winding of relay 124 so as to decrease the holding current of the relay and so as to avoid a slowed release of relay 124 when its circuit is opened by the removal of ground potential from the release-trunk conductor of the established connection. Upon the dialling of the remaining digits in the number, the connection is extended through the required number of switches to thecalled line.

Releasing `an established connection When `the subscriber at substation A1 repaces his receiver to release the connection, ground potential is removed from the releasetrunk conductor of the established connection, whereupon the switching relay 124 of the selector S1 falls back and the magnet 120 of lineswitch LS deenergizesto permit the armatures '106 and 107 to restore. When switching relay 124 of the selectory S1 falls back, it closes a circuit at its middle lower armature for release magnet 127 which includes off-normalspring 128 and the lower armature of relay 122. Release magnet 127 thereupon operates to restore the selector S1 to normal position, whereupon its circuit is opened at olf-normal spring 128.

Overflow at the selector S1 In case the selector S1, upon being operated in the usual manner, fails to find an idle trunk .line and continues to rotate until the wipers 133-135 pass beyond the last set of bank contacts, the overflow springs 125 yand 131 are operated. Overflow spring 125 substitutes busy-tone current Vfrom the busy-tone transformer 118 for the dial-tone current through the dial-tone transformer 117, `and overflow spring 131 opens the ground connecf tion to the lower terminal of the upper winding vof relay 123 and again connects the two windings of the relay in series, whereupon relay 123 reoperates from the release-trunk conductor v115, grounded at the inner-upper of the rotary magnet 129 at its lower armature so as to stop further rotation of the switch.

When the calling subscriber pauses in his dialling to listen in, he hears the busy-tone from the busy-tone transformer 118 and re, places his receiver. When this occurs, line relay 121 falls back and shunts release relay 122. Incidentally, magnet 126 is operated momentarily. Relay 122 falls back and removes the ground potential from releasetrunk conductor-115 at its upperarmature and again shunts the lower winding of relay 122. Relay 122 also falls back opening the circuit of magnet 126. The circuit of release magnet 127, as hereinbefore traced, is closed at the lower armature of relay'122 and the switch restores to normal position. The lineswitch LS releases inthe usual manner when the ground potential is removed from conductor 115.

Master-swatch operation Referringnow tothe figure the operation vof the master switch MS will now be explained. The power for operating the master switch is supplied by the solenoid 156, which upon operating rotates the master switch assembly in a clockwise direction to wind up the U spring 161, which U spring propels the master switch vin a counter-clockwise direction during the regular selecting action thereof, as shown, the solenoid 156 has just operated, and the U spring 161 is compressed to its maximum extent, the test wiper 162 being all the way over to the right and `standing on the contact associated with the tenth trunk leading to the selector S1.

With the selector S1 in the normal position shown, there is a battery potential impressed on release-trunk conductor 115 through the non-inductive upper winding of series relay 123, vertical off-normal contacts 132, and the inner upper armature of relay 122. With this battery potential on conductor 115, a l

switch segment 161, at the same time closing a circuit for the open-chain relay 153. The open-chain relay 153 operates and opens a further point in chain conductor 140, at the same time short-circuiting its upper winding so as to render lthe relay slow :to release. The

master switch is propelled in a clockwise direction by the U spring 161, until start relay 155 again operates upon an idle trunk being encountered. lVhen this occurs, the circuit of the locking magnet is opened and the rotation of the master switch is stopped. The open-chain relay falls back a moment later.

lVhen the trunk selecting operation has taken place until the test wiper 162 reaches the contact associated with trunk one, the master-switch linger 157 closes the contact spring 1.59, preparing a circuit for trip relay 151. The next time start relay 155 restores, trip relay 151 is operated in parallel with the locking magnet 152 through contacts 159. Upon operating, the trip relay 151 operates the associated latch, locking its contact asA4 sembly under the control of spring 160. At the outer contacts of trip relay 151, an additional circuit for the locking magnet 152 is closed, and at the inner contacts of relay 151 a circuit is closed for the solenoid 156. l/Vhcn the solenoid operates, the master switch is lnoved in a clockwise direction to the position shown in the drawing. The contacts 159 open the circuit of the trip relay 151 as soon as the movement Starts. The contacts of relay 151, however, remain locked under the control of spring 160, until spring 160 is moved by finger 158 of the master switch, when the master switch arrives in the position shown in the drawing. When this occurs, the circuit of solenoid 156 is opened and the alterna tive circuit of the locking magnet 152 is opened at the outer contacts of the trip relay.

In connection with the selector S1, it will be noted that relay 123, which restores at the end ot the primary operation of the selector S1, remains in a deenergized condition until the selector is again seized and reoperated. lith relay 123 deenergized, and with the vertical oft-normal contacts separated, the removal of ground potential from the releasetrunk conductor 115 to bring about the release ot' the connection does not cause the selector S1 to test idle to the master switch MS until the release magnet 127 has operated in the hereinbefore-described manner and restored the selector to its normal position. But, when the selector S1 reaches its normal position, off-normal contacts 132 close, therehy applying battery potential to conductor 115 through the upper winding of relay 123, so as to enable start relay 155 of the master switch MS to operate and stop the master switch on the selector S1., when the master switch is again operated to test this selector. By this arrangement. the master switch is prevented from stopping' on a selector' which is not in its normal position. Consequently, if a selector becomes stuck mechanically in an off-normal position, such selector' .is automatically cut out of service, and is not again seizedv by the master switch MS until ithas been repaired and restored to its normal position.

lVhat is claimed is:

1. In combination, a plurality of trunk lines, a plurality of non-numerical switchingr devices having access to said trunk lilies, a master switch arranged to mechanically operate said non-numerical switching devices in their selecting movements, said master switch having a start relay and cooperating circuits tor operating the master switch as long as the start relay is deenergized, and circuit connections for operating the start relay to terminate the movement of the master switch when an idle trunk line is encountered.

2. In a switching system wherein a master switch controls the selecting operation of a plurality of mechanically interconnected non-numerical switches, trunk lines accessible to said non-numerical switches, a control relay in said master switch and means for connecting the control relay to the test conductors of trunk lines with which the non-numerical switches are associated, and means ttor maintaining the non-numerical switches in association with a trunk line only as long as current flows from the test conductor thereof. through said control relay.

3. In combination, a group of lineswitches, a group of numerical switches accessible to said lineswitches, each ot said numerical switches having a normal position and a plurality ot off-normal positions, a master switch common to the lineswitches in said group and arranged to associate them with any idle one of said numerical switches, and means for preventing said master switch from associating said lineswitches with any idle one ot said numerical switches that is in an off-normal position.

4. ln a trunling system wherein a plurality of lineswitehes have access to a group ot uumerical switches, a master switch arranged to associate said lineswitches with any one of said numerical switches, said testing means in said master switch arranged so as to prevent said master switch normally from associating said lineswitches with any idle one of said numerical switches, each ot said niimerical switches having a plurality ot ofi'- normal positions and a normal position, means for restoring any numerical switch to its normal position, and means responsive to any numerical switch being restored to normal position for enabling said master switch to associate said lineswitches with such numerical switch.

5. In combination, a group of lineswitches having access to a group of selectors, cach oi said selectors having a pair ot off-normal contacts, a master switch and means for operating it to control the association of said lineswitches with said numerical switches, and means dependent upon the closure of a test circuit including said master switch and offnormal contacts of an idle numerical switch for stopping said master switch in association with such numerical switch.

6. In combination, a selector having ofi'- normal contacts closed when the selector is in normal position, lineswitches having access to said selector, a master switch having a test relay and arranged to control the selecting operation of said lineswitch, means for operating said master switch, and a circuit for stopping said master switch in association with said selector, said circuit including said off-normal contacts and said test relay in series.

In witness whereof, I hereunto subscribe my name this second day of March, A. D.

NORMAN H. SAUNDERS. 

